The present invention relates generally to fluid pumps, and, more specifically, to a pump configured for pumping blood in a living body.
The present invention is an improvement over the linear pump described in U.S. patent application Ser. No. 08/686,618; filed Jul. 19, 1996 now Pat. No. 5,924,975, and assigned to the present assignee. This type of linear pump includes a tubular piston mounted in a tubular housing for reciprocation therein. First and second check valves are joined to the housing and piston, respectively, for controlling fluid flow through the respective bores thereof for unidirectional flow. A linear motor is operatively joined between the piston and housing for periodically reciprocating the piston for in turn periodically pumping the fluid in unidirectional, pulsatile flow.
When used for pumping blood in a living body, the pump is surgically implanted near the heart for receiving blood from the left atrium and pumping it to the aorta as a left ventricular assist device (LVAD). A particular advantage of this linear pump is the hydrodynamic suspension of the piston within the housing using the pumping fluid or blood as a bearing fluid. The outer surface of the piston is spaced radially inwardly from the inner surface of the housing bore and is configured as either a linear or rotary hydrodynamic bearing for suspending the piston during reciprocation thereof, with minimum or no damage to the blood flowing therethrough.
Since the flowrate requirements of a natural heart vary for physiological reasons, the blood pump must be operated to correspondingly change the pumping flowrate therethrough. This is typically accomplished by varying the reciprocation frequency of the piston while utilizing the full stroke capability thereof. However, during operation the reciprocating piston causes corresponding vibration and movement of the pump which are undesirable when excessive.
Accordingly it is desired to reduce or eliminate vibration and movement of a blood pump implantable in a patient.